1. Field
Apparatuses and method consistent with the present disclosure relate to tomography apparatuses and methods of reconstructing a tomography image, and more particularly, to tomography apparatuses for reconstructing a tomography image by performing tomography scanning on a moving object and a method of reconstructing a tomography image.
2. Description of the Related Art
Medical imaging apparatuses are used to acquire images showing an internal structure of an object. The medical imaging apparatuses are non-invasive examination apparatuses that image details of structures, tissue, fluid flow, etc., inside a body and provide the images to a user. A user, e.g., a medical practitioner, may use medical images output from the medical imaging apparatuses to diagnose a patient's condition and diseases.
A computed tomography (CT) apparatus is a representative example of an apparatus for imaging an object by emitting X-rays toward a patient.
Among medical image processing apparatuses, a CT apparatus that is a tomography apparatus is capable of providing a cross-sectional image of an object. Furthermore, the CT apparatus may represent an internal structure (e.g., organs such as a kidney, a lung, etc.) of the object without superimposition of adjacent structures, as compared to a general X-ray apparatus. Due to these advantages, a CT apparatus is widely used for precise diagnosis of diseases. A medical image acquired by a tomography apparatus is hereinafter referred to as a tomography image.
A tomography apparatus performs tomography scanning on an object to acquire tomography data. The tomography data may be raw data, and the acquired raw data is used to reconstruct a tomography image. The raw data may be projection data obtained by projecting an X-ray onto the object, or may be sinogram data including a set of projection data.
For example, to obtain a tomography image, image reconstruction may be performed using sinogram data obtained by performing tomography scanning. Tomography image reconstruction will now be described in detail with reference to FIGS. 1A and 1B.
FIGS. 1A and 1B are diagrams for explaining imaging of a CT image.
In detail, FIG. 1A is a diagram for explaining a CT scan performed by a CT apparatus. During the CT scan, the CT apparatus acquires raw data while rotating around an object 25. FIG. 1B is a diagram for explaining sinogram data acquired during a CT scan and a CT image reconstructed from the sinogram data.
A CT apparatus generates and emits, via an X-ray generator, an X-ray towards an object, and detects, via an X-ray detector (not shown), the X-ray that has passed through the object. The X-ray detector may generate raw data corresponding to the detected X-ray.
In detail, referring to FIG. 1A, an X-ray generator 20 in a CT apparatus emits an X-ray towards the object 25. During a CT scan performed by the CT apparatus, as the X-ray generator 20 rotates around the object 25, and the X-ray generator 20 acquires a plurality of raw data sets 30, 31, and 32 corresponding to angles of rotation of the X-ray generator 20. In detail, the X-ray generator 20 acquires the plurality of the raw data sets 30, 31, and 32 by detecting X-rays emitted toward the object 25 at positions P1 through P3, respectively. In this case, a raw data set may be a projection data set.
To produce a cross-sectional CT image, the X-ray generator 20 may rotate 180 degrees, or more than 180 degrees.
Referring to FIG. 1B, sinogram data 40 may be acquired from the combination of the plurality of the raw data sets 30, 31, and 32 acquired by the X-ray generator 20 moving as described with reference to FIG. 1A. The sinogram data 40 is acquired by performing a CT scan in which the X-ray generator 20 rotates in one period. The sinogram data 40 corresponding to the one period may be used to produce a cross-sectional CT image. The one period may be a time period for the X-ray generator 20 to rotate 180 degrees or 360 degrees depending on specifications for a CT system.
A CT image 50 is reconstructed by performing filtered back-projection (FBP) on the sinogram data 40.
In general, it takes about 0.2 seconds for the X-ray generator 20 to rotate 180 degrees.
An object to be scanned may move during the one period of rotation. Due to the motion of the object, motion artifacts occur in a CT image.
FIG. 2 is a diagram for explaining motion artifacts present in a reconstructed CT image 200. In detail, FIG. 2 shows a CT image 200 obtained using a full reconstruction method in which an X-ray generator rotates around an object by an angle that is greater than or equal to 360 degrees.
Referring to FIG. 2, when motion artifacts occur in the reconstructed CT image 200, an outermost edge 220 of an object 210 may be unclear and overlapping with itself or others, and an inner edge 230 of the object 210 may be blurred due to movement of the object 210 in the CT image 200.
These motion artifacts in a CT image may reduce the quality of the CT image, and accordingly, analysis of an image and diagnosis of a disease by a user, e.g., a medical practitioner, may get harder.
In particular, if an object is a heart that contracts and relaxes quickly, there is a high probability of blurring or motion artifacts occurring in a CT image of the heart. Thus, blurring or motion artifacts need to be reduced in the CT image.
The degradation in quality of an image due to blurring or motion artifacts as described above becomes more severe when a C-arm CT is used. Recently, for treatment of vascular diseases such as stenosis, expansion, and occlusion, an interventional procedure under local anesthesia is favored compared to a surgical treatment. Thus, blurring or motion artifacts need to be reduced in a CT image generated by the C-arm CT